Authentic Meiji period original and authentic (c.1880), Japanese shunga erotic art woodblock prints.  It's a complete set of six different shunga clam/shellfish pictures, all analogies for the female vagina aside from the long clam (razor clam) which is the phallus reference.  A common motif in the 1800s often encountered in Japanese shunga picture books.   Four of the pictures are one type of clam or another, while the first shellfish featured with the spiky shell is a turbin-shelled snail (sazae).  The last one shown in the group is abelone (awabi).
These pictures here are actuallly miniature woodblock print envelopes.  They come inside a larger ukiyo-e casing with a Japanese beauty on the cover fetching clams in the shallows.  Larger shunga case measures 15.4 cm x 16.1 cm when fully opened up.  The envelope pictures each measure 3.4 cm x 4.2 cm and are in wonderfully pristine condition!  Very good colors and impressions.  No backing.  Please see and judge from photos. 
 
This is a very odd and rare set of sexually connotative artwork from the latter 1800s Japan.  These would definitely fall under the shunga trick-picture-oddity theme.  So seemingly innocent, yet explicitly sexual in nature, even their casing.  A truly scarce shunga set that will have you never looking at shellfish the same way again!